Today when users start Elasticsearch with their Java configuration
pointing to a pre-Java 8 install, they encounter a cryptic message:
Exception in thread "main" java.lang.UnsupportedClassVersionError:
org/elasticsearch/bootstrap/Elasticsearch : Unsupported major.minor
version 52.0
They often think that they have Java 8 installed but if their JAVA_HOME
or other configuration is causing them to start with a pre-Java 8
install, this error message does not help them.
We introduce a Java version checker that runs on Java 6 as part of the
startup scripts. If the Java version is pre-Java 8, we can display a
helpful error message to the user informing them of the Java version
that the runtime was started with. Otherwise, Elasticsearch starts as it
does today.
Ryan Ernst
Jason Tedor